1. Field of the Invention
The present invention relates to a method and apparatus for determining an optimum power of a laser beam incident on a recording medium.
2. Discussion of the Related Art
A variety of storage discs are now available. For example, disc types now include Digital Versatile Disc (DVD), Blu-ray Disc (BD), and High-Density DVD (HD-DVD). Information can be written onto and read from the disc via a recording/reproducing device. Further, the storage discs are generally classified into read-only discs and recordable discs.
Further, the recording/reproducing device illuminates a laser beam with relatively-high energy and that changes a material characteristics of a record layer of the recordable disc, so that information or data can be recorded on the optical disc. In addition, the data recording/reproducing device reproduces information or data from the optical disc using a laser beam with relatively-low energy incapable of changing the material characteristics of the record layer.
In other words, during a recording mode, the recording/reproducing device drives a laser diode (LD) at a relatively high power, and forms pits on the optical disc, so that information or data is recorded in the pits of the optical disc. The recording/reproducing apparatus transmits a relatively low power laser beam onto the disc, and reads the information stored on the disc based on an amount of light reflected from the disc (i.e., the reproducing apparatus determines whether the data on the disc is a 1 or 0 binary data based on the reflected light).
Further, each disc may require different laser powers. Therefore, the data recording/reproducing device searches information on the disc for an optimum laser power, and uses the optimum laser power to record data on the disc. The operation for searching for the optimum laser power is generally called “Power Calibration” or “Optimum Power Control (OPC)”.
Further, the recordable disc includes a test area that is used for the OPC process. The data recording/reproducing device records a test signal in the test area, reproduces the recorded test signal, and compares the reproduced test signal with a predetermined reference value, thereby deciding an optimum laser power.
However, due to defects of the test area and/or data throughput problems for the recording/reproducing device, the related art recording/reproducing device has difficulty in effectively performing the OPC process. In addition, when the OPC process is incorrectly performed, the data recording/reproducing device cannot record data at an optimum laser power, so that data is not recorded on the disc. Further, even if the data is recorded on the disc, the data recording/reproducing device cannot accurately reproduce the recorded data.